4.4.5. Films' ORA

The Wang et al. [49] technique was slightly modified to determine the ORA of the films. In a hot-air oven set at 50 ◦C, the filter paper (6 cm in diameter) was dried to a consistent weight. The film samples (4 cm × 4 cm) were placed upside down on the filter paper for 48 h while being secured with ropes on the top of glass test tubes containing 5 mL of oil. After 48 h, the filter paper was weighed, and the oil absorption rate (OAR) was determined using the equation

$$\text{OAR } (\%) = \frac{\text{W} - \text{W1}}{\text{W1}} \times 100 \tag{3}$$

where W is the weight of filter paper after 48 h and W1 is the weight of dried filter paper.
